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Postmenopausal women experience bone loss and weight gain. To date, crosstalk between estrogen receptor signals and nuclear factor-κB (NF-κB) has been reported, and estrogen depletion enhances bone resorption by osteoclasts via NF-κB activation. However, it is unclear when and in which tissues NF-κB is activated after menopause, and how NF-κB acts as a common signaling molecule for postmenopausal weight gain and bone loss. Therefore, we examined the role of NF-κB in bone and energy metabolism following menopause. NF-κB reporter mice, which can be used to measure NF-κB activation in vivo, were ovariectomized (OVX) and the luminescence intensity after OVX increased in the metaphyses of the long bones and perigonadal white adipose tissue, but not in the other tissues. OVX was performed on wild-type (WT) and p65 mutant knock-in (S534A) mice, whose mutation enhances the transcriptional activity of NF-κB. Weight gain with worsening glucose tolerance was significant in S534A mice after OVX compared with those of WT mice. The bone density of the sham group in WT or S534A mice did not change, whereas in the S534A-OVX group it significantly decreased due to the suppression of bone formation and increase in bone marrow adipocytes. Disulfiram, an anti-alcoholic drug, suppressed OVX-induced activation of NF-κB in the metaphyses of long bones and white adipose tissue (WAT), as well as weight gain and bone loss. Overall, the activation of NF-κB in the metaphyses of long bones and WAT after OVX regulates post-OVX weight gain and bone loss., Competing Interests: Declaration of competing interest The authors have declared no conflict of interest., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The AP-1 transcription factor JunB plays crucial roles in multiple biological processes, including placental formation and bone homeostasis. We recently reported that JunB is essential for development of Th17 cells, and thus Junb-deficient mice are resistant to experimental autoimmune encephalomyelitis. However, the role of JunB in CD4 + T cells under other inflammatory disease conditions is unknown. Here we show that mice lacking JunB in CD4 + T cells (Junb fl/fl Cd4-Cre mice) were more susceptible to dextran sulfate sodium (DSS)-induced colitis because of impaired development of regulatory T (Treg) cells. Production of interleukin (IL)-2 and expression of CD25, a high affinity IL-2 receptor component, were decreased in Junb-deficient CD4 + T cells in vitro and in vivo. Naive CD4 + T cells from Junb fl/fl Cd4-Cre mice failed to differentiate into Treg cells in the absence of exogenously added IL-2 in vitro. A mixed bone marrow transfer experiment revealed that defective Treg development of Junb-deficient CD4 + T cells was not rescued by co-transferred wild-type cells, indicating a significance of the cell-intrinsic defect. Injection of IL-2-anti-IL-2 antibody complexes induced expansion of Treg cells and alleviated DSS-induced colitis in Junb fl/fl Cd4-Cre mice. Thus JunB plays a crucial role in the development of Treg cells by facilitating IL-2 signaling.

Approximately 70% of breast cancer cells express oestrogen receptor alpha (ERα). Previous studies have shown that the Brefeldin A-inhibited guanine nucleotide-exchange protein 3-prohibitin 2 (BIG3-PHB2) complex has a crucial role in these cells. However, it remains unclear how BIG3 regulates the suppressive activity of PHB2. Here we demonstrate that BIG3 functions as an A-kinase anchoring protein that binds protein kinase A (PKA) and the α isoform of the catalytic subunit of protein phosphatase 1 (PP1Cα), thereby dephosphorylating and inactivating PHB2. E2-induced PKA-mediated phosphorylation of BIG3-S305 and -S1208 serves to enhance PP1Cα activity, resulting in E2/ERα signalling activation via PHB2 inactivation due to PHB2-S39 dephosphorylation. Furthermore, an analysis of independent cohorts of ERα-positive breast cancers patients reveal that both BIG3 overexpression and PHB2-S39 dephosphorylation are strongly associated with poor prognosis. This is the first demonstration of the mechanism of E2/ERα signalling activation via the BIG3-PKA-PP1Cα tri-complex in breast cancer cells.

Smad1, Smad5 and Smad9 (also known as Smad8) are activated by phosphorylation by bone morphogenetic protein (BMP)-bound type I receptor kinases. We examined the role of Smad1, Smad5, and Smad9 by creating constitutively active forms (Smad(DVD)). Transcriptional activity of Smad9(DVD) was lower than that of Smad1(DVD) or Smad5(DVD), even though all three Smad(DVD)s associated with Smad4 and bound to the target DNA. The linker region of Smad9 was sufficient to reduce transcriptional activity. Smad9 expression was increased by the activation of BMP signaling, similar to that of inhibitory Smads (I-Smads), and Smad9 reduced BMP activity. In contrast to I-Smads, however, Smad9 did not inhibit the type I receptor kinase and suppressed the constitutively active Smad1(DVD). Smad9 formed complexes with Smad1 and bound to DNA but suppressed the transcription of the target gene. Taken together, our findings suggest that Smad9 is a new type of transcriptional regulator in BMP signaling.

Xanthohumol (XN) is a natural anticancer compound that inhibits the proliferation of oestrogen receptor-α (ERα)-positive breast cancer cells. However, the precise mechanism of the antitumour effects of XN on oestrogen (E2)-dependent cell growth, and especially its direct target molecule(s), remain(s) largely unknown. Here, we focus on whether XN directly binds to the tumour suppressor protein prohibitin 2 (PHB2), forming a novel natural antitumour compound targeting the BIG3-PHB2 complex and acting as a pivotal modulator of E2/ERα signalling in breast cancer cells. XN treatment effectively prevented the BIG3-PHB2 interaction, thereby releasing PHB2 to directly bind to both nuclear- and cytoplasmic ERα. This event led to the complete suppression of the E2-signalling pathways and ERα-positive breast cancer cell growth both in vitro and in vivo, but did not suppress the growth of normal mammary epithelial cells. Our findings suggest that XN may be a promising natural compound to suppress the growth of luminal-type breast cancer.

Transducing-like enhancer of split 3 (TLE3), one of the Groucho/TLE family members, targets Runx2 transcription and suppresses osteoblast differentiation in bone marrow stromal cells (BMSCs). Here, we identify Wnt responsive elements of the TLE3 promoter region through comparative genomic and functional analyses and show that expression of TLE3 is increased by Wnt signaling, which is important for osteoblast differentiation. We also demonstrated that TLE3 is able to suppress canonical Wnt signaling in BMSCs. Taken together, our data suggest that induction of TLE3 by Wnt signaling is part of a negative feedback loop active during osteoblast differentiation., (Copyright © 2014 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.)

Bone morphogenetic proteins (BMPs) are multifunctional cytokines that belong to the transforming growth factor-β family. BMPs were originally identified based on their unique activity, inducing heterotopic bone formation in skeletal muscle. This unique BMP activity is transduced by specific type I and type II transmembrane kinase receptors. Among the downstream pathways activated by these receptors, the Smad1/5/8 transcription factors appear to play critical roles in BMP activity. Smad1/5/8 transcription factors are phosphorylated at the C-terminal SVS motif by BMP type I receptors and then induce the transcription of early BMP-responsive genes by binding to conserved sequences in their enhancer regions. The linker regions of Smad1/5/8 contain multiple kinase phosphorylation sites, and phosphorylation and dephosphorylation of these sites regulate the transcriptional activity of Smad proteins. Gain-of-function mutations in one BMP type I receptor have been identified in patients with fibrodysplasia ossificans progressiva, a rare genetic disorder that is characterized by progressive heterotopic bone formation in the skeletal muscle. The mutant receptors activate the Smad signaling pathway even in the absence of BMPs, therefore novel inhibitors for the BMP receptor - Smad axis are being developed to prevent heterotopic bone formation in fibrodysplasia ossificans progressiva. Taken together, the data in the literature show that the BMP type I receptor - Smad signaling axis is the critical pathway for the unique activity of BMPs and is a potential therapeutic target for pathological conditions caused by inappropriate BMP activity.

Bone morphogenetic proteins (BMPs) inhibit myogenesis and induce osteoblastic differentiation in myoblasts. They also induce the transcription of several common genes, such as Id1, Id2 and Id3, in various cell types. We have reported that a GC-rich element in the Id1 gene functions as a BMP-responsive element (BRE) that is regulated by Smads. In this study, we analyzed and identified BREs in the 5'-flanking regions of the mouse Id2 and Id3 genes. The core GGCGCC sequence was conserved among the BREs in the Id1, Id2 and Id3 genes and was essential for the response to BMP signaling via Smads. We found a novel BRE on mouse chromosome 13 at position 47,723,740-47,723,768 by searching for conserved sequences containing the Id1 BRE. This potential BRE was found in the 5'-flanking region of a novel gene that produces a non-coding transcript, termed BMP-inducible transcript-1 (BIT-1), and this element regulated the expression of this gene in response to BMP signaling. We found that BIT-1 is expressed in BMP target tissues such as the testis, brain, kidney and cartilage. These findings suggest that the transcriptional induction of the Ids, BIT-1 and additional novel genes containing the conserved BRE sequence may play an important role in the regulation of the differentiation and/or function of target cells in response to BMPs.

Bone morphogenetic proteins (BMPs) bind to two types of membrane receptors. Type II receptor phosphorylates type I receptor, then the phosphorylated type I receptor phosphorylates downstream effectors, such as Smads. Fibrodysplasia ossificans progressiva (FOP) is a rare autosomal dominant disorder characterized by progressive heterotopic ossification in skeletal muscle tissue. ALK2, a BMP type I receptor has been mutated in patients with FOP. The mutant ALK2 phosphorylates Smads in the absence of BMPs. In FOP, muscle injury may enhance BMP signaling via Smads to induce acute heterotopic ossification. Inhibitors of the BMP-Smad pathway will be useful to develop novel treatments for FOP.

Smads 1/5/8 transduce the major intracellular signaling of bone morphogenetic proteins (BMPs). In the present study, we analyzed Smad1-binding proteins in HEK293T cells using a proteomic technique and identified the protein, zinc-finger, RAN-binding domain-containing protein 2 (ZRANB2). Zranb2 interacted strongly with Smad1, Smad5, and Smad8 and weakly with Smad4. The overexpression of Zranb2 inhibited BMP activities in C2C12 myoblasts in vitro, and the injection of Zranb2 mRNA into zebrafish embryos induced weak dorsalization. Deletion analyses of Zranb2 indicated that the serine/arginine-rich (SR) domain and the glutamine-rich domain were required for the inhibition of BMP activity and the interaction with Smad1, respectively. Zranb2 was found to be localized in the nucleus; however, the SR domain-deleted mutant localized to the cytoplasm. The knockdown of endogenous Zranb2 in C2C12 cells enhanced BMP activity. Zranb2 suppressed Smad transcriptional activity without affecting Smad phosphorylation, nuclear localization, or DNA binding. Taken together, these findings suggested that Zranb2 is a novel BMP suppressor that forms a complex with Smads in the nucleus., (Copyright © 2011 Wiley Periodicals, Inc.)

MicroRNAs (miRNAs) play critical roles in a variety of biological processes in diverse organisms, including mammals. In the mouse skeletal system, a global reduction of miRNAs in chondrocytes causes a lethal skeletal dysplasia. However, little is known about the physiological roles of individual miRNAs in chondrocytes. The miRNA-encoding gene, Mir140, is evolutionarily conserved among vertebrates and is abundantly and almost exclusively expressed in chondrocytes. In this paper, we show that loss of Mir140 in mice causes growth defects of endochondral bones, resulting in dwarfism and craniofacial deformities. Endochondral bone development is mildly advanced due to accelerated hypertrophic differentiation of chondrocytes in Mir140-null mice. Comparison of profiles of RNA associated with Argonaute 2 (Ago2) between wild-type and Mir140-null chondrocytes identified Dnpep as a Mir140 target. As expected, Dnpep expression was increased in Mir140-null chondrocytes. Dnpep overexpression showed a mild antagonistic effect on bone morphogenetic protein (BMP) signaling at a position downstream of Smad activation. Mir140-null chondrocytes showed lower-than-normal basal BMP signaling, which was reversed by Dnpep knockdown. These results demonstrate that Mir140 is essential for normal endochondral bone development and suggest that the reduced BMP signaling caused by Dnpep upregulation plays a causal role in the skeletal defects of Mir140-null mice.

We previously reported an important role of RQCD1 in mammary carcinogenesis through the interaction with Grb10 interacting GYF protein 1 (GIGYF1), Grb10 interacting GYF protein 2 (GIGYF2) and growth factor receptor binding protein 10 (Grb10). In this study, we investigated the biological mechanism of RQCD1 in regulation of the Akt activity as the downstream signal of epidermal growth factor receptor (EGFR). Knockdown of RQCD1 reduced the Akt phosphorylation level that was induced by epidermal growth factor (EGF) stimulation. We found a possible formation of the big complex involved in the Akt activity including Akt, EGFR, GIGYF1 and GIGYF2, Grb10 and RQCD1. We subsequently defined that a region corresponding to 620-665th amino acids of GIGYF1 and 667-712th amino acids of GIGYF2 interacted with RQCD1. Furthermore, we found that RQCD1 was required for enhancement of the interaction of Grb10 with GIGYF1 and GIGYF2. Our findings in this study imply the functional mechanism of RQCD1 in the Akt activity regulation as a mediator in the EGFR-signaling pathway.

Fibrodysplasia ossificans progressiva (FOP) is a rare autosomal dominant disorder characterized by progressive heterotopic bone formation in skeletal muscle tissue. In 2007, FOP was authorized as one of the Intractable Disorders by the Ministry of Health, Labour and Welfare of Japan. The Research Committee on FOP is working on the molecular mechanisms underlying heterotopic bone formation and the development of new treatments for FOP.

Phosphorylation of Smad1/5/8 at carboxyl-terminal serine residues by type I receptors activates downstream bone morphogenetic protein (BMP) signaling. Protein phosphatase magnesium-dependent 1A (PPM1A) has been shown to suppress BMP activity by dephosphorylating phospho-Smads. We report here that PPM1A suppresses BMP signaling via a novel mechanism. PPM1A inhibited a constitutively activated Smad1 mutant lacking BMP receptor phosphorylation sites. PPM1A reduced the protein levels not only of Smad1 but also of Smad5 and Smad8. A proteasome inhibitor blocked the inhibitory effects of PPM1A on Smad1, but the Smurf-binding motif in the Smad1 linker region was not involved in this inhibition. The phosphatase activity of PPM1A is essential for inhibition. Taken together, these findings suggest that through the dephosphorylation of unidentified substrate(s), PPM1A inhibits BMP signaling by decreasing Smad protein levels via the proteasome pathway. Moreover, knockdown of endogenous PPM1A stimulated osteoblastic differentiation, suggesting that PPM1A may physiologically suppress BMP signaling via Smads., (Copyright 2010 American Society for Bone and Mineral Research.)

Bone morphogenetic proteins (BMPs) induce not only bone formation in vivo but also osteoblast differentiation of mesenchymal cells in vitro. Tumor necrosis factor alpha (TNFalpha) inhibits both osteoblast differentiation and bone formation induced by BMPs. However, the molecular mechanisms of these inhibitions remain unknown. In this study, we found that TNFalpha inhibited the alkaline phosphatase activity and markedly reduced BMP2- and Smad-induced reporter activity in MC3T3-E1 cells. TNFalpha had no effect on the phosphorylation of Smad1, Smad5, and Smad8 or on the nuclear translocation of the Smad1-Smad4 complex. In p65-deficient mouse embryonic fibroblasts, overexpression of p65, a subunit of NF-kappaB, inhibited BMP2- and Smad-induced reporter activity in a dose-dependent manner. Furthermore, this p65-mediated inhibition of BMP2- and Smad-responsive promoter activity was restored after inhibition of NF-kappaB by the overexpression of the dominant negative IkappaBalpha. Although TNFalpha failed to affect receptor-dependent formation of the Smad1-Smad4 complex, p65 associated with the complex. Chromatin immunoprecipitation and electrophoresis mobility shift assays revealed that TNFalpha suppressed the DNA binding of Smad proteins to the target gene. Importantly, the specific NF-kappaB inhibitor, BAY11-7082, abolished these phenomena. These results suggest that TNFalpha inhibits BMP signaling by interfering with the DNA binding of Smads through the activation of NF-kappaB.

Patients with classic fibrodysplasia ossificans progressiva, a disorder characterized by extensive extraskeletal endochondral bone formation, share a recurrent mutation (R206H) within the glycine/serine-rich domain of ACVR1/ALK2, a bone morphogenetic protein type I receptor. Through a series of in vitro assays using several mammalian cell lines and chick limb bud micromass cultures, we determined that mutant R206H ACVR1 activated BMP signaling in the absence of BMP ligand and mediated BMP-independent chondrogenesis that was enhanced by BMP. We further investigated the interaction of mutant R206H ACVR1 with FKBP1A, a glycine/serine domain-binding protein that prevents leaky BMP type I receptor activation in the absence of ligand. The mutant protein exhibited reduced binding to FKBP1A in COS-7 simian kidney cell line assays, suggesting that increased BMP pathway activity in COS-7 cells with R206H ACVR1 is due, at least in part, to decreased binding of this inhibitory factor. Consistent with these findings, in vivo analyses of zebrafish embryos showed BMP-independent hyperactivation of BMP signaling in response to the R206H mutant, resulting in increased embryonic ventralization. These data support the conclusion that the mutant R206H ACVR1 receptor in FOP patients is an activating mutation that induces BMP signaling in a BMP-independent and BMP-responsive manner to promote chondrogenesis, consistent with the ectopic endochondral bone formation in these patients.

We here report identification and characterization of required for cell differentiation 1 homolog (RQCD1) as a potential therapeutic target for breast cancer. Gene-expression profiling analysis of breast cancer cells, semi-quantitative RT-PCR, Northern blotting and Western blotting confirmed RQCD1 to be frequently up-regulated in breast cancer specimens and breast cancer cell lines. On the other hand, its expression was very weak or hardly detectable in normal human tissues except testis, indicating this molecule to be a novel cancer-testis antigen. Treatment of breast cancer cell lines with siRNA targeting RQCD1 drastically suppressed cell proliferation. Concordantly, introduction of exogenous RQCD1 into HEK293 cells significantly enhanced cell growth, implying RQCD1 to have an oncogenic activity. Co-immunoprecipitation experiments and immunocytochemical staining revealed an interaction of RQCD1 protein with Grb10 interacting GYF protein 1 (GIGYF1) and 2 (GIGYF2) proteins, involved in regulation of Akt activation, in breast cancer cells. Interestingly, knockdown of either of RQCD1, GIGYF1 or GIGYF2 resulted in significant reduction of the phosphorylation of Akt at Ser 473 in breast cancer cell lines. Our findings suggest that RQCD1 is a potential molecular target for treatment of breast cancer.

Bone morphogenetic proteins (BMPs) induce osteoblastic differentiation of myoblasts via binding to cell surface receptors. Repulsive guidance molecules (RGMs) have been identified as BMP co-receptors. We report here that DRAGON/RGMb, a member of the RGM family, suppressed BMP signaling in C2C12 myoblasts via a novel mechanism. All RGMs were expressed in C2C12 cells that were differentiated into myocytes and osteoblastic cells, but RGMc was not detected in immature cells. In C2C12 cells, only DRAGON suppressed ALP and Id1 promoter activities induced by BMP-4 or by constitutively activated BMP type I receptors. This inhibition by DRAGON was dependent on the secretory form of the von Willbrand factor type D domain. DRAGON even suppressed BMP signaling induced by constitutively activated Smad1. Over-expression of neogenin did not alter the inhibitory capacity of DRAGON. Taken together, these findings indicate that DRAGON may be an inhibitor of BMP signaling in C2C12 myoblasts. We also suggest that a novel molecule(s) expressed on the cell membrane may mediate the signal transduction of DRAGON in order to suppress BMP signaling in C2C12 myoblasts.

Fibrodysplasia ossificans progressiva (FOP) is a rare autosomal dominant disorder characterized by congenital malformation of the great toes and by progressive heterotopic bone formation in muscle tissue. Recently, a mutation involving a single amino acid substitution in a bone morphogenetic protein (BMP) type I receptor, ALK2, was identified in patients with FOP. We report here that the identical mutation, R206H, was observed in 19 Japanese patients with sporadic FOP. This mutant receptor, ALK2(R206H), activates BMP signaling without ligand binding. Moreover, expression of Smad1 and Smad5 was up-regulated in response to muscular injury. ALK2(R206H) with Smad1 or Smad5 induced osteoblastic differentiation that could be inhibited by Smad7 or dorsomorphin. Taken together, these findings suggest that the heterotopic bone formation in FOP may be induced by a constitutively activated BMP receptor signaling through Smad1 or Smad5. Gene transfer of Smad7 or inhibition of type I receptors with dorsomorphin may represent strategies for blocking the activity induced by ALK2(R206H) in FOP.

We previously reported that Frizzled homologue 10 (FZD10), a member of the Wnt signal receptor family, was highly and specifically upregulated in synovial sarcoma and played critical roles in its cell survival and growth. We here report a possible molecular mechanism of the FZD10 signaling in synovial sarcoma cells. We found a significant enhancement of phosphorylation of the Dishevelled (Dvl)2/Dvl3 complex as well as activation of the Rac1-JNK cascade in synovial sarcoma cells in which FZD10 was overexpressed. Activation of the FZD10-Dvls-Rac1 pathway induced lamellipodia formation and enhanced anchorage-independent cell growth cells. FZD10 overexpression also caused the destruction of the actin cytoskeleton structure, probably through the downregulation of the RhoA activity. Our results have strongly implied that FZD10 transactivation causes the activation of the non-canonical Dvl-Rac1-JNK pathway and plays critical roles in the development/progression of synovial sarcomas.

We present experimental results indicating involvement of cyclic AMP (cAMP)-mediated signaling in bone morphogenetic protein (BMP)-induced osteoblastic gene expression at the transcriptional level by luciferase activity assay in C2C12 cells using the promoter sequence of the Id1 gene, an early-response gene to BMPs, which contains both a BMP-responsive element (BRE) and a cAMP-response element (CRE). In cells transfected with luciferase gene driven by wild-type Id1 promoter, treatment with BMP-4 increased luciferase expression, which was further enhanced by the addition of dibutyryl cAMP (dbcAMP). This dbcAMP-enhanced luciferase expression was significantly suppressed when the CRE site in the Id1 promoter was replaced by mutated CRE or endogenous CRE-binding protein (CREB) was knocked down by transfection of CREB RNAi. Pretreatment of cells with protein kinase A (PKA) inhibitor, H89, also dramatically reduced dbcAMP-enhanced luciferase expression. Immunoprecipitation assay showed phosphorylated-Smad1/5/8, phosphorylated-CREB, and CREB-binding protein (CBP) formed the transcriptional complex. These data indicate that cAMP-PKA/CREB/CRE signaling potentially enhances BMP-induced transcription through the BRE in the promoter of the BMP-responsive gene through a PKA-mediated pathway.

Loss of function of the Wnt co-receptor, lipoprotein receptor-related protein 5, decreases bone formation, and a point mutation in this gene results in high bone mass, indicating the importance of this signaling pathway in bone formation. However, the exact mechanism is currently unknown. We examined a potential role for Wnt signaling and functional cross-talk of bone morphogenetic protein 2 (BMP-2) in osteoblast differentiation. To assess the contribution of Wnt, we generated C2C12 cells over-expressing Wnt3a or Wnt5a and treated these with BMP-2. We showed that expression of matrix extracellular phosphoglycoprotein was induced by BMP-2 in Wnt3a over-expressing C2C12 cells but not in Wnt5a over-expressing C2C12 cells. Over-expression of Wnt3a blocked BMP-2-induced inhibition of myotube formation in C2C12 cells when switched to low mitogen medium. In these cultures, expression of inhibitor of DNA binding/differentiation (Id) 1, a helix-loop-helix protein induced by BMP-2, decreased in stable Wnt3a- but not in Wnt5a-expressing cells. This suppression is mediated by a GC-rich region of the BMP-2-responsive element of the Id1 gene promoter, and interaction between Smad1/4 and beta-catenin is crucial for Wnt-mediated suppression of the BMP-2 response in C2C12 cells. Over-expression of the inhibitor of canonical Wnt signaling, Dickkopf, inhibits this suppression. In contrast, BMP-2 or Smad1/4 up-regulated Wnt3a or activated beta-catenin-induced lymphoid-enhancing factor 1/T cell factor-dependent transcriptional activity. These findings identify functional cross-talk of Id1 expression between Wnt and BMP signaling and demonstrate a novel mechanism for Wnt regulation of the BMP-2 response, linking Id1 expression to Wnt/beta-catenin signaling.

It has been shown that Emdogain Gel (Emd-Gel) containing enamel matrix proteins promotes biomineralization, such as osteogenesis and cementogenesis, during the regeneration of periodontal tissues. However, the growth factors involved in these activities of Emd-Gel remain unclear. In this study, Emd-Gel was fractionated into 22 sub-fractions by size exclusion chromatography. The osteoinductive factors, TGF-beta and BMP, were examined by a specific luciferase reporter gene assay. In the unfractionated Emd-Gel, TGF-beta-like activity was detected, while BMP activity was not. In contrast, in the fractionated Emd-Gel samples, TGF-beta-like activity was detected from fractions 8 to 13, and BMP-like activity was detected from fractions 4 to 6. Also, it was confirmed that the BMP-like activity in Emd-Gel was inhibited by authentic TGF-beta1 and TGF-beta-like activity. These results indicate that Emd-Gel contains both TGF-beta- and BMP-like growth factors that contribute to the induction of biomineralization during periodontal regeneration.

In the present study, genomic differences related to sensitivity to radiation were examined by comparative genomic hybridization and GeneChip 45K microarray in SX9 cells (radiation-sensitive) and their parental line, SR-1 (radiation-resistant). SX9 cells have defective DNA-dependent protein kinase catalytic subunit (DNA-PKcs) activity. DNA-PKcs is a DNA double-strand break repair protein that maintains chromosomal stability through nonhomologous end joining. However, the molecular basis of the radiation sensitivity of SX9 cells is unclear. Flow cytometry analysis showed that SR-1 and SX9 cells had a larger G2/M-phase population at 12 h after 4 Gy gamma irradiation, while only SR-1 cells progressed to G1/S at 24-36 h. SX9 and SR-1 cells had similar patterns of DNA copy number alteration, but the gains were observed on chromosome 9 (cent-E2), 11 (cent-A3), and 12 (C1-E) only in SX9 cells. Expression of genes located on those regions is higher in SX-9 cells than in SR1 cells, and the regions include genes associated with apoptosis and cell cycle regulation. Time-course data for gene expression at 0, 1, 3, 6 and 12 h after 4 Gy gamma irradiation revealed that the genes whose expression was altered in SX9 cells but not in SR-1 cells are in 16 clusters. Three of these clusters included genes for cell cycle regulation: JNK, PKC (PRKC) and ceramide cascade protein. These results suggest that amplification and altered expression of genes associated with cell cycle and apoptosis regulators in DNA-PK-deficient SX9 cells affect the differences in response to gamma radiation between SX9 and SR-1 cells.

Purpose: Synovial sarcoma is a soft tissue sarcoma, the growth regulatory mechanisms of which are unknown. We investigated the involvement of fibroblast growth factor (FGF) signals in synovial sarcoma and evaluated the therapeutic effect of inhibiting the FGF signal., Experimental Design: The expression of 22 FGF and 4 FGF receptor (FGFR) genes in 18 primary tumors and five cell lines of synovial sarcoma were analyzed by reverse transcription-PCR. Effects of recombinant FGF2, FGF8, and FGF18 for the activation of mitogen-activated protein kinase (MAPK) and the growth of synovial sarcoma cell lines were analyzed. Growth inhibitory effects of FGFR inhibitors on synovial sarcoma cell lines were investigated in vitro and in vivo., Results: Synovial sarcoma cell lines expressed multiple FGF genes especially those expressed in neural tissues, among which FGF8 showed growth stimulatory effects in all synovial sarcoma cell lines. FGF signals in synovial sarcoma induced the phosphorylation of extracellular signal-regulated kinase (ERK1/2) and p38MAPK but not c-Jun NH2-terminal kinase. Disruption of the FGF signaling pathway in synovial sarcoma by specific inhibitors of FGFR caused cell cycle arrest leading to significant growth inhibition both in vitro and in vivo. Growth inhibition by the FGFR inhibitor was associated with a down-regulation of phosphorylated ERK1/2 but not p38MAPK, and an ERK kinase inhibitor also showed growth inhibitory effects for synovial sarcoma, indicating that the growth stimulatory effect of FGF was transmitted through the ERK1/2., Conclusions: FGF signals have an important role in the growth of synovial sarcoma, and inhibitory molecules will be of potential use for molecular target therapy in synovial sarcoma.

Background: Bone morphogenetic protein-2 (BMP-2) stimulates osteoblast differentiation, but inhibits myogenic differentiation in C2C12 myoblasts. BMP-2 induces transcription of Id1, an inhibitor for myogenesis, within 1 h in the cells. To examine the molecular mechanism of the action of BMP-2, we analysed a BMP-2-responsive element (BRE) in the 5' flanking region of the human Id1 gene., Results: A GC-rich region between -985 bp and -957 bp of the human Id1 gene was identified as a BRE. The BRE containing promoter activity was stimulated by BMP-2 or by constitutively active BMP receptors (BMPR-IA and BMPR-IB). The stimulation was blocked by co-transfecting with dominant negative BMPR-IA or Smad7. A unique DNA-protein complex was induced in response to BMP-2 on the BRE. The complex induced by BMP-2 contained Smad1 and Smad4, possibly as a complex of both Smads. BMP-2 failed to stimulate the expression of Id1 mRNA in Smad4-deficient cells. Over-expression of Smad4, but not Smad1, stimulated the Id1 reporter activity and the expression of endogenous Id1 mRNA in Smad4-deficient cells., Conclusion: Signalling of BMP-2 to stimulate the expression of Id1 would be transduced by BMPR-IA and mediated by Smad1 and Smad4, both of which form a complex on the 29 bp GC-rich element.

TGFbeta inducible early gene (TIEG) is a novel Krüppel-like transcriptional repressor that was recently shown to increase the activity of the TGFbeta/Smad signal transduction pathway by relieving negative feedback through repression of the inhibitory Smad7. Interestingly, while Smad7 is required for maximal enhancement of TGFbeta/Smad signaling, we observe that TIEG is still capable of increasing Smad pathway activity in the absence of Smad7. Furthermore, while Smad7 is known to block both TGFbeta and bone morphogenetic protein (BMP) signaling, we observe that TIEG specifically enhances only the TGFbeta pathway. Similarly, while both TIEG and the related Krüppel-like factor, FKLF2, repress Smad7 transcription, only TIEG is capable of enhancing Smad signaling. In order to identify additional regulatory targets of TIEG important for this enhancement of the Smad pathway activity, we performed microarray analysis and identified Smad2 as a TIEG target gene. We now show evidence that TIEG increases transcription of the Smad2 gene but not the Smad3 or Smad4 genes. Furthermore, while the TGFbeta/Smad pathway remains intact in Smad2 null cells, TIEG enhancement of Smad signaling is dramatically reduced. Thus we propose a new model whereby TIEG enhances Smad signaling by a dual mechanism involving both the repression of the inhibitory Smad7 as well as the activation of Smad2., (Copyright 2002 Wiley-Liss, Inc.)

Signaling events leading to B cell growth or apoptosis are beginning to be unravelled, but detailed information is still lacking. To identify signaling molecules involved in B cell antigen receptor (BCR)-initiated pathways, we used the immature B cell line, WEHI-231, to investigate protein tyrosine phosphatases (PTP) whose expression was modulated by BCR ligation. Among the PTP cloned by reverse transcription-PCR, mRNA expression of the proline-, glutamic acid-, serine- and threonine-rich (PEST) domain phosphatase (PEP) was selectively elevated 3.1-fold within 3 h after anti-IgM antibody stimulation. In contrast, expression of another PEST domain phosphatase, PTP-PEST, was unaffected. Western blot analysis revealed that 71% of PEP was located in the cytosolic fraction, while 29% was in the membrane fraction. To examine the direct contribution made by PEP to BCR-initiated signal transduction, we transfected an antisense PEP cDNA into WEHI-231 cells. Two stable clones were established in which PEP expression was reduced by 34% and 47%, respectively. Strikingly, BCR-mediated inhibition of DNA synthesis was significantly rescued in the clones, and G1 phase cell cycle arrest and apoptosis were almost completely ablated. Considered collectively, these results indicate that PEP is a positive, crucial regulator in determining B cell fate triggered by BCR engagement.

Bone morphogenetic protein-2 (BMP-2) inhibits terminal differentiation of C2C12 myoblasts and converts them into osteoblast lineage cells (Katagiri, T., Yamaguchi, A., Komaki, M., Abe, E., Takahashi, N., Ikeda, T., Rosen, V., Wozney, J. M., Fujisawa-Sehara, A., and Suda T. (1994) J. Cell Biol. 127, 1755-1766). In the present study, we examined the possible involvement of Smad proteins, vertebrate homologues of Drosophila Mothers against decapentaplegic, in the BMP effects on the differentiation of C2C12 myoblasts. C2C12 cells expressed Smad1, Smad2, Smad4, and Smad5 mRNAs, and expression levels were not altered by treatment with BMP-2 or TGF-beta1. When Smads were transiently transfected into C2C12 cells, both Smad1 and Smad5 induced alkaline phosphatase (ALP) activity and decreased the activity of myogenin promoter/chloramphenicol acetyltransferase (myogenin-CAT) without BMP-2. When C-terminal-truncated Smad1 and Smad5 were transfected into constitutively active BMP receptor type IB (BMPR-IB)-expressing C2C12 cells, BMP signals were blocked, resulting in an increase in myogenin-CAT activity. On the other hand, Smad1 and Smad5 decreased myogenin-CAT activity but did not induce ALP activity in MyoD-transfected NIH3T3 fibroblasts. These results suggest that both Smad1 and Smad5 are involved in the intracellular BMP signals which inhibit myogenic differentiation and induce osteoblast differentiation in C2C12 cells, and that the conversion of the two differentiation pathways is regulated independently at a transcriptional level., (Copyright 1997 Academic Press.)

Bone morphogenetic protein-2 (BMP-2), a member of transforming growth factor-beta superfamily, inhibits the terminal differentiation of C2C12 myoblasts and changes their differentiation pathway into cells expressing osteoblast phenotypes such as alkaline phosphatase (ALP) activity and osteocalcin production (Katagiri et al., 1994, J. Cell Biol. 127, 1755-1766). Two type I receptors for BMP-2 (BMPR-IA and BMPR-IB) have been cloned, but the role of the respective receptors in signal transduction is not clear. In the present study, we examined the signal transduction of BMP-2 in C2C12 cells using constitutively activated mutant BMPR-IA and BMPR-IB. C2C12 cells expressed BMPR-IA and BMPR-II mRNAs, but not BMPR-IB mRNA at detectable levels in Northern blotting. When mutated BMPR-IA and BMPR-IB were transiently transfected into C2C12 cells, both BMPR-IA and BMPR-IB similarly induced ALP activity in the absence of BMP-2. We also established subclonal cell lines of C2C12 cells by stably transfecting mutated BMPR-IB. When the mutated BMPR-IB-transfected cells were cultured in medium with low serum (differentiation medium) without BMP-2, the cells differentiated into ALP-positive mononuclear cells and not into myosin heavy chain-positive myotubes. These mutated BMPR-IB-transfected cells expressed ALP activity and osteocalcin mRNA in a time-dependent manner, but neither muscle creatine kinase nor myogenin mRNAs. These results indicate that the mutated BMP-2 type I receptors can constitutively transduce BMP-2 signals in the absence of the ligand in C2C12 cells.

Members of the transforming growth factor (TGF)-beta superfamily bind the transmembrane serine/threonine kinase complex consisting of type I and type II receptors. Their intracellular signals are propagated via respective type I receptors. Bone morphogenetic protein (BMP)-2, a member of the TGF-beta superfamily, induces ectopic bone formation when implanted into muscular tissues. Two type I receptors (BMPR-IA and BMPR-IB) have been identified for BMP-2. We have reported that BMP-2 inhibits the terminal differentiation of C2C12 myoblasts and converts their differentiation pathway into that of osteoblast lineage cells (Katagiri, T., Yamaguchi, A., Komaki, M., Abe, E., Takahashi, N., Ikeda, T., Rosen, V., Wozney, J. M., Fujisawa-Sehara, A. and Suda, T. (1994) J. Cell Biol. 127, 1755-1766). In the present study, we examined the involvement of functional BMP-2 type I receptors in signal transduction in C2C12 cells, which expressed mRNA for BMPR-IA, but not for BMPR-IB in Northern blotting. TGF-beta type I receptor (TbetaR-I) mRNA was also expressed in C2C12 cells. Subclonal cell lines of C2C12 that stably expressed a kinase domain-truncated BMPR-IA (DeltaBMPR-IA) differentiated into myosin heavy chain-expressing myotubes but not into alkaline phosphatase (ALP)-positive cells, even in the presence of BMP-2. In contrast, the differentiation of the DeltaBMPR-IA-transfected C2C12 cells into myotubes was suppressed by TGF-beta1, as in the parental C2C12 cells. BMP-2 did not efficiently suppress the mRNA expression of muscle-specific genes such as muscle creatine kinase, MyoD, and myogenin, nor did it induce the expression of ALP mRNA in the DeltaBMPR-IA-transfected C2C12 cells. In contrast, TGF-beta1 inhibited mRNA expression of the muscle-specific genes in those cells. When wild-type BMPR-IA was transiently transfected into the DeltaBMPR-IA-transfected C2C12 cells, a number of ALP-positive cells appeared in the presence of BMP-2. Transfection of wild-type BMPR-IB or TbetaR-I failed to increase the number of ALP-positive cells. These results suggest that the BMP-2-induced signals, which inhibit myogenic differentiation and induce osteoblast differentiation, are transduced via BMPR-IA in C2C12 myoblasts.

Protein tyrosine kinase p59fyn is associated with the TCR-CD3 complex and is suggested to play a role in T cell activation. To determine the molecular mechanism of p59fyn-mediated signal transduction in T cell activation, we established murine T cell hybridoma lines that expressed an elevated amount of wild-type or mutant fyns. Clones that expressed high levels of normal p59fyn and active p59fyn, encoded by wild-type and f-14 mutant fyn respectively, showed enhanced IL-2 production upon stimulation by anti-CD3 antibodies or natural antigen. On the other hand, clones that expressed kinase negative p59fyn and p59fyn with an SH2 (Src-homology 2) deletion encoded by t-1 mutant fyn showed little induction of IL-2 production upon stimulation. These data suggest that p59fyn is important in T cell signaling and that the SH2 sequence plays a critical role in the reaction. Induction of tyrosine phosphorylation of multiple proteins upon antigenic stimulation was augmented similarly in the cells that respectively expressed wild-type and f-14 mutant fyns at elevated levels. The proteins that became highly tyrosine-phosphorylated included phospholipase C (PLC-gamma 1), p95vav, ZAP-70, the MAP kinase, CD3 zeta and unidentified proteins of 120, 100 and 80 kDa. Tyrosine phosphorylation of the 120, 95 and 68 kDa proteins associated with PLC-gamma 1 was also observed in these cells upon stimulation. In contrast, only the 100 kDa protein and the MAP kinase were increasingly tyrosine phosphorylated in the antigen-stimulated cells expressing t-1 fyn. These data suggest that PLC-gamma 1, PLC-gamma 1 associated molecules, p95vav, the 80 kDa protein, ZAP-70 and the CD3 zeta chain may be substrates of p59fyn or of other tyrosine kinases regulated by p59fyn and be important in T cell signaling.